This specification relates to optical devices and more specifically to magneto-optic switches.
There are a large number of various types of optic switches, all aiming to achieve light beam switching between one input optical fiber and multiple output optical fibers or between multiple input optical fibers and one output optical fiber. Optic switches are typically used in the optical fiber communication industries, instrument industries, and defense industries.
Typical optic switches are primarily divided into mechanical optic switches and non-mechanical optic switches. Mechanical types of optic switch technologies have advantages including low production cost, broad bandwidth and low optical loss, etc. However, they also suffer from drawbacks including a large size, short life, poor repeatability, slow switching, etc. Advantages of non-mechanical optic switches include no moving part(s), high repeatability, high reliability, and fast switching, etc. A magneto-optical Switch is one type of non-mechanical optical switch. However, conventional non-mechanical optical switches have drawbacks including high optical insertion loss and high production cost due to their complex configuration and stringent optical alignment process.
FIG. 1 is a structural diagram of a conventional magneto-optic switch 100. An optical fiber 12 is installed in optical fiber collimator 11. Along a direction of a light path, the magneto-optic switch 100 includes a birefringent crystal 13, half wave plate assembly 14, Faraday rotator element 16, birefringent optic crystal plate 17, birefringent optic crystal light beam deflector 18, Faraday rotator element 19, half wave plate assembly 21, birefringent optic crystal 22, and dual fiber optical collimator 23 are positioned in sequence. Two parallel optical fibers 24 are installed in dual fiber optical collimator 23. Outside of Faraday rotator elements 16 and 19, magnetic field generating component 15 and 20 are separately positioned.
After a light beam is emitted from the optical fiber 12 of the single fiber optical collimator 11, it forms two light beams with identical directions of propagation after passing through the birefringent optic crystal 13. The polarization states of the two light beams are perpendicular to each other. After the two light beams pass through the half wave plate assembly 14, the directions of propagation remain unchanged, but the polarization states are identical. Furthermore, the two light beams pass through the Faraday rotator element 16, causing polarization states experience a rotation.
Particularly, when linear polarized light with a fixed polarization state passes through the Faraday rotator element 16, its polarization state rotates differently depending on a direction of the magnetic field. The birefringent optic crystal plate 17 and birefringent optic crystal light beam deflector 18 have different optical index of refraction for light beams with different polarization states. Thus, after light beams with different polarization states pass through birefringent optic crystal plate 17 and birefringent optic crystal light beam deflector 18, their directions of propagation will experience different changes. Using this characteristic, and by changing the direction of the current of the coil in magnetic field generating component 15, the magneto-optic switch changes the magnetic field polarity generated by the magnetic field generating component 15. This further changes the polarization states of light beams passing through the Faraday rotator element 16, and changes the directions of propagation of light beams after they pass through the birefringent optic crystal plate 17 and the birefringent optic crystal light beam deflector 18.
After light beams pass through the birefringent optic crystal plate 17 and the birefringent optic crystal light beam deflector 18, sequentially, they pass through the Faraday rotator element 19 and half wave plate assembly 21, before being emitted to the birefringent optic crystal 22. The two light beams that pass through the half wave plate assembly 21 merge into one beam inside the birefringent optic crystal 22, and then are emitted out of the optical fiber 24 inside the dual fiber optical collimator 23.
Because a change of the magnetic field polarity generated by the magnetic field generating component 15 can change the directions of propagation of light beams passing through the birefringent optic crystal plate 17 and the birefringent optic crystal light beam deflector 18, it is possible to select which optical fiber 24 inside the dual fiber optical collimator 23 the light beams will be directed toward, thus providing selection of a light path resulting in optical switching.
Additionally, the optical fibers installed in the single fiber optical collimator 11 and the optical fibers 12 and 24 installed in the dual fiber optical collimator 23 are ordinary standard optical fibers, thus the light beam being emitted from the optical fiber 12 has a large beam radius and a significant beam divergence, requiring the use of relatively bulky birefringent optic crystals 13 and 22. Thus, the Faraday rotator elements 16 and 19, birefringent optic crystal plate 17, and birefringent optic crystal light beam deflector 18 can all be relatively bulky. Additionally, it may be necessary to place certain clearances between the birefringent optic crystal plate 17 and the birefringent optic light beam deflector 18, making it difficult to reduce the sizes of the Faraday rotator elements 16 and 19, birefringent optic crystal plate 17, and birefringent optic crystal light beam deflector 18.
In addition, the magnetic field generating components 15 and 20 normally include a coil wound iron core, on which coils are wound. Because the Faraday rotator elements 16 and 19, birefringent optic crystal plate 17, and birefringent optic crystal light beam deflector 18 are relatively bulky, it can be difficult to place the components in the same iron core. The use of two magnetic field generating components 15 and 20 is typically required to respectively load magnetic fields into the Faraday rotator elements 16 and 19, leading to a higher number of components used by magneto-optic switches and bulkier components. This can raise the production cost of magneto-optic switches and increase the packaging difficulty.